mitchell



(No Model.)

2 Sheets-Sheet 1. l

J. MITCHELL.

FURNAGE,

Paten-tedot. 20, 1891.

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J. MITCHELL. FURNAGE.

No. 461,444. Patented Oct. 20, 1891.

Rg. a.

UNITED' 'STATES PATENT OFFICE.

JOHN MITCHELL, OF ROCHESTER, NEWT- YORK, ASSIGNOR TO CLARKS COKING i AND SMOKELESS FURNACE COMPANY, OF SAME PLACE.v

FU RNACE.

SPECIFICATION forming part of -Letters Patent No. 461,444, dated October 20, 18.91. Application led December 24, 1890. Serial No. 375,715. (No model.)

To .all whom t may concern:

Be it known that I, JOHN MITCHELL, a citizen of the United States, residing at Roches- A ter, New York, have inventedv certain Improvements in Furnaces, of which the following is a specification, reference being had to the accompanying drawings.

My invention relates to certain improvements in furnaces for steam-boilers, whereby ro the production of smoke is prevented and inf creased efficiency is secured along with durability and cheapness of construction.

My improvements are fully described and illustrated in the following specification and I5 the accompanying drawings, and the novel features thereof speciiied in the claims anneXed to the said speciication.- Y

In the accompanying drawings, representing a steam-boiler furnace embodying my im- 2o provenients, Figure 1 is an elevation, the front of the furnace being removed. Fig. 2 is a transverse section on the line 2 2, Fig. Fig. 3 is a plan. Fig. 4 is a central longitudinal section. In the accompanying drawings, representing my improved furnace as applied to a steam-boiler, A is the boiler; B, the front grate, on which the coal is partially burned or coked; C, the rear grate, on which the com- 3o bustion is completed; D, the bridge-wall, and E E', the descending-dues, through which the volatile or gaseous products of the combustion on the front gate are conveyed underneath the rear grate, so as to secure their 3 5 complete combustion by passing upward through the incandescent material thereon. The grates are placed on the same horizontal level, or so that the combustible can be transferred from the front to the rear grate, and 4o an opening Fis formed in the bridge-wall immediately above the grates through which the coked or partially-burned coal is transferred from the front to the rear grate. In practical use the coal is kept piled up on the front grate, so as to close or partially close the opening F, thereby compelling the gases and volatile matters to pass into the flues E E through openings G G in the bridge-wall. Provision is made for admitting air under- 5'o neath the rear or secondary grate through a suitable draftopening provided with a damper. The boiler is of any ordinary type provided with the return-fines H.

The side Walls I I of the boiler-setting are constructed in any ordinary way of dimensions suitable to the size of the boiler, and the rear wall J is placed at such a distance from the rear end of the boiler as to permit the products of combustion to pass upward and enter the flues II.

K is the front of the boiler, provided with the usual doors, and L the uptake.

The' bridge wall is provided below the grat-es with a door M, through which the ashes are removed from underneath the secondary grate. .The opening F in the bridgewall above the grate' is preferably made in theA form of an arch, constructed of any suitable iire-brick N, which are set in two rows with broken joints, as indicated by the full 7o and dotted lines in Fig. l, so that in case one or more of the bricks in one row should be broken or crack off the arch will still bepreserved by the bricks of the other row, so that there is no gap or opening through which air or gases can obtain access directly to the combustion-space above the secondary grate without passing throughr the flues E E. Above the arch the bridge-wall is `continued ,all the way up to the lower side of the boiler 8o or other surface which it is designed to heat, except that the openings G Gl are formed in the wall, through which the gaseous products A of the primary combustion obtain access from above the front grate to the descending fines E E,'which open into the space underneath the secondary grate. Air is admitted under the secondary grate through a suitable passage provided with a regulating valve or damper.l This passage for a single boiler is 9a arranged at one side, as 'indicated at O, Fig. 2, or for a battery of boilers may be placed in the bridge-wall below the grates, as shown at O', Fig. 1, or may enter from the rear, as at O, Fig. 3. Y

The flues E E are built of brick or in any other suitable way, being closed on all sides, except as they are providedv with the openings G G', and are open at their lower ends into the space below the secondary grate. Ioo At the inner sides the fiues are formed by the walls P P', which separate the iiues from the combustion-chamber above the secondary grate. The rear walls of the ilues Q Q extend upward to the boiler.

At its rear side the secondary combustionchamber communicates with the passage R Aunderneath the boiler and through which the fiame and hot gases pass to the ues H.

It will be observed that under certain circumstances or for small furnaces one ofr the descending lues may be dispensed with, the remaining one being made of sufficient dimensions to conduct away the gaseous products from the primary fire. It will also be obvious that other changes may be made in the construction and arrangement-such, for instance, as inclining the descending flue or locating it outside the side wall or at the side of the front grate-without departure from the principle involved therein. My improved furnace may also be applied to purposes other than heating boilers.

In the operation of my improved furnace, the coal, which has been coked or partially burned on the primary grate, is pushed backward from time to time onto the secondary grate through the openingin the bridge-wall, so as to keep the rear grate uniformly covered with a layer -of incandescentcombustible. Under these circumstances the combustion on the secondary grate is perfect and the smoke or gas from the partial combustion on the primary grate is entirely consumed in passing through the fire on the secondary grate, as I have demonstrated by practical use extend* ing over a considerable period of time. In practice I have found the following proportions satisfactory for a boiler four feet in diameter: front grate, forty inches by forty inches; secondary grat-e, twenty-one inches by thirty inches, and flues nine inches by twenty-one inches.

@cking-chambers, arranged at the side of a grate and of the combustion-chamber and pro'- vided with a conduit for gases, extending across the front of and above said grate, were known prior to my invention. In such construction the coke could be poked out onto the grate. The inner wall of the coking- Achamber was liable to be speedily burned out. By my construction the coking-chamber is placed in front and the grate C directly behind it, the interposed bridge-Wall being provided with suitable opening, being so related to the two grates that the coke can be pushed through the front door directly back onto the rear grate; and, further, the gases from the coking coal are, together with air for combustion, delivered directly under the rear grate and at both sides thereof, thus more thoroughly distributing them and avoiding also the obstruction of the front of the grate by the conduit above referred to.

I olaiml. The combination, in a furnace, of the primary grate B and secondary grate C, arranged one in front of the other to permitthe transfer of the combustible from the primary to the secondary grate, and separated from each other by the wall D, having opening F immediately above the grates, one or more descending flues E, constituting a communi-l cating passage between'the chamber above the primary grate and the space below the secondary grate, and a suitable air-inlet passage through which air is supplied to the combustion on the secondary grate, substantially as described.

2. The combination, in a furnace, of'the primary and secondary gratos B and C, the intermediate bridge-wall D, having im mediately above the grates the opening F, provided along its upper edge with the double row of fire-brick N, arranged with .broken joints, and a passage or iiue communicating between the chamber over the primary grate and the spacev underneath the secondary grate, substantially as described.

3L The combination, in a furnace, of the primary grate B and secondary grate C, arranged one in front of the other to permit the transfer of the combustible from the primary to the secondary grate, and separated from each other by the wall D, having open-ing F immediately above the grates, and the openings G G in the upper part of the wall, the descending fines E E', arranged onzopposte sides of 'the secondary grate, and a suitable air-inlet passage through which air is supplied to the secondary grate, substantially as described.

JOHN MITCHELL. lVitnesses:

. W. RIDER,

GEO. B. SELDEN. 

